As far as I know its all about hitting the nodes of the hamonic series
And when you fret a note they stay the same just get shorter in distance depending how high you’re fretting.
I would say in improvising it’s really hard to keep track of. But if you know you wana hit a harmonic at a certain point it really is just about fretting that note, finding where on the string you need to pinch and memorize it for that particular part of the song.
So memorizeing where it is for that particular note probably is the only simple way. Idk?
I think I see zakk wylde often doing the same pinch harmonics he’s memorized for a certain key, I’ve not really looked into that though.
Once you’re past the 12th fret it’s a lot easier to judge the half way point and roughly go for that one.
That could be a technique to use? Practice judging that halfway pint of your fretted note, that gives you a platform to go a bit away from half way and get others. Gives a starting framework for visualisation atleast.
I wonder if there is a pinch harmonic pedal, just hit the pedal and get a harmonic lol
I also wonder is you could use a decent elastic band and mark it, it would probably stretch to the right points, tho I’m sure it works better in my imagination than real life